The present invention relates to a disc cartridge, for example, a magnetic disc cartridge or an optical disc cartridge, which rotatably accommodates a disc for recording information therein in a cartridge case, and more specifically, to an apparatus for producing a disc cartridge provided with a shutter, made of a synthetic resin, for opening and closing a aperture formed in the cartridge case for inserting a head there through.
A disc cartridge of this kind is already known, an example of which is shown in FIG. 5 in the form of a disassembled perspective view of the cartridge.
FIG. 5 shows a magnetic disc cartridge, in which a flexible magnetic disc 2 is rotatably accommodated in a cartridge case 1 constructed by connecting an upper case 1a and a lower case 1b both made of a synthetic resin. The magnetic disc 2 is formed with a hub 3 at the central portion thereof, which is exposed to the outside through a hole 4 formed at the center of the cartridge case 1. Through this hub 3, the magnetic disc 2 is rotated at a predetermined speed by a driving device.
The above-mentioned cartridge case 1 is formed with rectangular apertures 5, for allowing access of a magnetic head to the disk 2, on the upper and lower surfaces thereof at predetermined positions. About the peripheral region of each of the apertures 5 is formed a shallow recess 6 of a rectangular shape, to which a shutter 7 having a U-shaped cross-section is slidably fitted.
The shutter 7 comprises two flat plate portions 9a, 9b opposing each other and an end plate portion 10 connecting the flat plate portions 9a, 9b with each other at respective edges thereof, and is formed with rectangular windows 8 having almost the same size and shape as the apertures 5. The shutter 7 when mounted on the cartridge can is kept elastically urged by means of a built-in spring (not shown) towards a position such that the apertures 5 are closed. When the shutter 7 is moved against the elastic force of the spring, and is stopped by the stepped portion of the recess 6, the apertures 5 and the windows 8 are registered or aligned with each other and the apertures 5 are opened, thereby making it possible to insert a magnetic head for access to the disk 2.
The shutter 7 is made from metal or a synthetic resin. In the case of metal, the sliding surface of the recess 6 may be scratched by the edges of the shutter 7 when the shutter slides over the surface of the recess 6, and there may be produced scratched chips of synthetic resin which may be deposited on or adhered to the magnetic disc and which are apt to cause errors in recording or in reproducing. When, for preventing this trouble, a large clearance is arranged between the cartridge case 1 and the shutter 7, dust may easily intrude from the outer circumference through the peripheral region of the shutter 7 and may adhere to or be deposited on the magnetic disc 2, thereby also causing errors in recording and reproducing.
On the other hand, in the case when the shutter is made from synthetic resin, there is no problem relating to the scratching of the surface of the recess 6, in contrast to the case when the shutter is made from metal. Therefore, the shutter 7 can be elastically pressed so as to be in close contact with the surface of the cartridge case 1 (recess 6), and the intrusion of dust from the peripheral region of the shutter 7 can be effectively prevented. However, there is still another problem.
The motion of the shutter 7 is limited by stepped portions of the recess 6 of the cartridge case 1. However, when the shutter 7 is shaped such that the flat plate portions 9a, 9b extend as diverging outwards, as shown in FIG. 6A showing a side view of the shutter 7, the end A is widely opened, and the flat plate portions 9a, 9b may ride over the stepped portions, thus allowing the shutter 7 to be moved beyond the limited movable range thereof. As a result, there occurs a problem that a positional deviation is produced between the opening portion or aperture 5 and the window 8, and it become impossible to insert a magnetic head in a suitable manner.
The same problem occurs when the flat plate portions 9a, 9b, which were parallel to each other at the time of fabrication, suffer deformations due to repeated use, and the open end A opens even wider, as shown in FIG. 6A.
Further, when the shutter is so shaped that the flat plate portions 9a, 9b converge towards the open end a as shown in FIG. 6B showing a side view of the shutter 7, there occurs a problem that the open end A become extremely narrow, and the sliding resistance between the shutter 7 and the recess 6 of the cartridge case 1 undesirably increases.
Therefore, it is desirable from a point of view relating to the functional features of the shutter such as movable range-controllability or slide resistance that the flat plate portions of the shutter slightly contact or are convergent to be close to each other with a slight gap therebetween at the free ends, i.e. open end A of the shutter 7.
However, it is not easy to fit the shutter 7 having a contacting open end A as mentioned above to the recess 6 of the cartridge case 1.
Therefore, there is required a fitting process. In one of the conventional processes, opening jigs are inserted through the open lateral sides B and moved towards the open end a relative to the shutter 7, to open the end A and then the shutter 7 fitted to the recess 6 of the cartridge case 1 with the open end A maintained in a relatively widely opened condition. In another conventional process, the flat plate portions 9a, 9b are both pulled outwards by sucking forces of a vacuum suction device, and the shutter 7 fitted to the recess 6 of the cartridge case 1 with the shutter maintained in a relatively widely opened condition.
In the above-mentioned conventional apparatus, in order to fit a shutter 7, having an open end A slightly contacting or slightly opened, to the cartridge case 1, it was required to use opening jigs or a vacuum suction device. As a result, the work for mounting or fitting the shutter became complex and required a long time, thereby deteriorating the efficiency of the work.